1. Field of the Invention
The present invention relates to a thermal printer, and more specifically to mounting structure of a thermal head.
2. Description of the Prior Arts
There has been known a thermal printer which records an image on a recording paper line by line with use of a thermal head while transporting the recording paper in a sub-scanning direction. The thermal head is provided with a head substrate and a heating element array provided in the head substrate. In the heating element array, plural heating elements are arranged along a main scanning direction. Both ends in the main scanning direction of the head substrate are held by a pair of support plates. Each heating element of the thermal head is driven in response to printing data to generate heat in accordance with recording density.
Heat energy generated from the heating element is partially transferred to the head substrate. The heat is further transferred to the support plate contacting with the both ends of the head substrate. As shown in FIG. 6, the temperature of the both ends of the thermal head (head substrate) tends to become lower than the central portion thereof. Accordingly, since the temperature of the head substrate is not uniform, there has been a problem that density unevenness is caused in the recorded image.
Japanese Patent Laid-Open Publication No. 6-143652 discloses a printer in which printing data is corrected based on virtual data that estimates heat quantity at the both ends of the thermal head. In this printer, the printing data is corrected in consideration of a temperature decrease at the both ends of the thermal head, so that the density unevenness in the recorded image caused by temperature unevenness in the head substrate is prevented.
However, since a memory for storing the virtual data and a correction circuit for correcting the printing data based on the virtual data are required, there is a problem that the printer is complicated to increase the cost.